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66 cuda' with 318/340 HiPo cam and heads,won't run right,HELP!!

Discussion in 'Performance' started by john slawsky, Nov 7, 2015.

  1. john slawsky

    john slawsky New Member

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    I am posting this for a friend, he has a 1966 cud' that he totally restored with the help of his Brother. They have the car 99.9% done, but ran into a brick wall....
    First the car
    1966 Baracuda, has a totally rebuilt 318 with 340 heads and a 340 HiPo camshaft, edelbrock 500 cfm carb ( my opinion, a little small), dual exhaust and "H" pipe,with factory manifolds and I think edelbrock intake, also has been converted to newer style distributor and ecu electronic ignition and new coil, not sure if running resistor, regapped plugs and i believe 7mm wires...the car originaly sounded awesome sitting still, then they took it to be inspected, alignment done and asked mechanic to tune the carb...
    Mechanic told him that no matter what he did to carb it made no difference to how engine ran and that there was some other problem, had to leave it to be diagnosed...they took car back...its been a 4 year resto and they're trying to diagnose ...
    first, they couldn't time engine correctly,then timing seemed to jump around...replaced advance springs, but now dist. is at full advance at 1800 rpms (springs too light i guess)...he changed the ecu,and coil, car has absolutely no power at all,running super rich and timing way off...
    His brother is so pissed off, he wants to pull the hipo cam and replace with stock cam.....this car is painted,polished,interior done,it was tune it and take it to the show.....now so desperate to tune it, want to pull a camshaft....please help.....I have done a ton of reading and the 340 heads and hipo cam are said to be a very nice set up, but somethings very wrong, and I'm not convinced its the camshaft,,,,,any advice would be appreciated...thanks in advance..
     
  2. john slawsky

    john slawsky New Member

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    sorry, its a comp cams, thumper camshaft...
     
  3. ImperialCrown

    Level III Supporter

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    Welcome to Allpar. You said that the technician 'couldn't make any difference in the way it ran by trying to adjust the carburetor' and that it is 'running rich'.
    That suggests to me that the carb is possibly dumping gas into the engine? Do you see drips or a stream of gas from the venturis at idle? Are the spark plug tips fouling black? If you introduce a vacuum leak, does it seem to run better?
    I say check the carb first. There may be more uncovered as you diagnose and remedy items.
     
    Bearhawke likes this.
  4. Locodave

    Locodave Member

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  5. Locodave

    Locodave Member

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    An after thought on the vacuum advance. During the start of the emission years. Un-shure on this if Dodge did this also. Somewhere around the mid 70's. I've run across a vacume retard instead of being an advance. Or a dual port can. If you used a late model dizzy. I would check it to make shure it's doing what you want it to do. Centrifugal weights you already found an issue with. Working with the vacuum advance.
     
  6. hemirunner426

    Level 2 Supporter

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    Was the cam Degree'd in?
     
  7. dana44

    Ad-Free Member

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    Total timing in by 1800 is definitely springs too light, try the medium and the light, sounds like two light springs, usually full advance around 2800-3000rpm for small blocks. Next, problem may be the carb, float level, needle out of its seat. Next thing is vacuum. What is a vacuum gauge doing? Is it steady or does it bounce around? I personally don't like using the 340/360 heads on a 318 unless the pistons are at 0 or .010 deck height, it drops the compression quite a bit, and then the thumpr cam on top of that, so check the compression. This cam should be something in the 150psi or higher, lower doesn't work very well with big cams. One last thing that wasn't mentioned was the heads. Were they shaved any amount to raise the compression? If more than .010, the valves can be staying slightly open or pumping up, bleeding off compression too fast (and making the timing jump around even more), but the good thing is, they make rocker arm shims to go under the pedistals to get them back where they belong, or, adjustable rockers and matching pushrods (my choice always with a cam this large).
    Check the compression first, then move to the carb checks.
     
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  8. Mike V.

    Mike V. Mopar-nac The Moderator
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  9. pt006

    pt006 Active Member

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    John; the ECU system requires a resistor. Get the timing to stop jumping around first, and go from there.
     
  10. MoparDanno

    Level III Supporter

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    2 or 3 things right off the top of my head.

    First off, do you know the @ .050" specs on that cam? Edelbrock carbs don't like low vacuum cams at all, and unless you know how to tune the idle system for them they will just run either super lean or super rich depending on the actual vacuum reading.

    Second, the vacuum port that you have the vacuum advance hooked to is critical. If you have it to a ported spot ( IE only vacuum when the throttle is open ) then the advance curve is going to be all over the place. Make sure that you have a solid manifold vacuum source for your vac advance.

    Odds are that the dist he went with is a MP piece. If this is the case, then you have to be careful about TOO much advance on them. You need a certain amount of initial to get the car running right depending on the combo, and the mechanical advance in the dist is added on top of that. I have seen the MP distributors ADDING as much as 38 degrees of mechanical advance. If you are starting at 10 advanced ( pretty typical ) and you get 38 more degrees... well you do the math.

    Where are you located?
     
  11. chargermike

    chargermike Active Member

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    I would work on getting the timing fixed first. Make sure weights in the dist aren`t sticking or hanging up. I agree that the Mopar Performance dist has too much advance built in and the springs are way too light. You can weld up the slots to adjust. Try leaving the vacuum advance disconnected and plugged off and set the initial timing and see what the total advance is. A lot of people put a collar on the dist shaft at the drive gear to keep the timing from bouncing around..
     
  12. pt006

    pt006 Active Member

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    John; Most 318 engines had a nylon timing chain camshaft gear which would go bad with miles and/or time. If bad, it is better to replace it with a double roller. Which lasts longer and maintains its accuracy longer. Double roller chains became standard in trucks in the late '80's, and were also in some HP small blocks back in the 60's.

    I'd use the stock centrifugal advance springs to get a base reading and then tune from there.
     
  13. dana44

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    Have you done a compression test yet? 360 heads on 318s tend to have lower compression and bigger cams with greater duration are then worse than stock cams more times than not, the larger chambers in the 360 kills compression, 318 heads with 1.88 intake valves is the ticket, or flat topped pistons that give you zero deck height to raise compression up to about 8.4:1 (tops) with 360 heads helps. Also, a matching intake to the larger port heads is important so the ports match better.

    I would hope a roller or at least new stock timing chain was installed when the new cam was installed.
     
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  14. AC TC

    AC TC Well-Known Member

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    And you can adopt the magnum type chain guides on the la engine, a good modification.
     
  15. dartndodge

    dartndodge Well-Known Member

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    As dana44 says, you dont have enough compression. What pistons were used? Was the deck height checked and block squared up? 318s can run hard but need lots of compression. With the big chamber 340 heads and the big cam your 318 lost its compressing ability and would be a dog. If he used "replacement" 8.5 :1 pistons, this would be even worse. Unless he is a serious drag racer and therefore would have short gears and loose converter, then 340 heads and big cam are a waste of time (ie if he has a 500cfm carb, he is no racer). Find some non cracked mid 70s 318 heads, do a mild port and shine job, replace the 1.5" exhaust valves with 1.6" valves, blend in the exhaust, remove bad castings and humps. Dont grind the floor of Mopar heads, but mild grind the short turn radius and the roof, port match intakes/exhaust to gasket/manifold as close as practical.
    With your low comp, run a mild cam, a 360 cam works nice, something around 252deg and 260deg for a street mild teen. If you have more comp....say 10.5 you can run a 270-280deg cam with gears and converter. Teens need air velocity not volume, because of the small stroke and small bore.
    Junk the carb and put on a built Thermoquad.
    Port the manifold to improve flow by cleaning up daggy castings etc.
    You will have a much nicer street engine going milder not hotter.
    Hope this helps.
     
  16. dartndodge

    dartndodge Well-Known Member

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    Oh I forgot to mention....even better heads are the Swirl port 80s/90s heads, Magnum heads are also good, but need oil mod (pushrods). 340 heads are overkill.
     
  17. dana44

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    Using Magnum heads requires heads, valve covers, intake manifold, exhaust manifolds are recommended (they breathe better and the ports match better), AMC V8 lifters and I think the Magnum pushrods (they have oiling holes in them), then the pushrod holes need to be drilled out larger to accept the offset of the lifter spacing compared to the LA blocks, but they do work, there is a slight boost in compression, have 1.92 intakes which is needed and good for breathing. There are plenty of articles on this swap.

    On the 318 heads, the exhaust valves are OK, it is the intakes that need increase. Stock 1.88 340/360 intake valves (to keep the cost down) can have the seats ground and the port then blended like a tulip or inverted bell shaped to really breathe well. And for the record, 2.02 intakes fit the 318 bore, but a little overkill.
     
  18. Volunteer

    Volunteer Well-Known Member

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    Maybe I'm wrong but I thought the Magnum engines were 'rollerized' - like the last five or so years of the 'LA' - meaning long (tall) lifters and short push-rods.
    Also, if the ignition conversion is from MP (including that nasty looking orange ECM) then the internal curve specs are good as-is. Not sure if you mean that the full centrifugal is all in by 1800 engine RPM's OR distributor (cam) RPM's. Big difference. Full advance by 1800 engine revs will not only produce significant 'rattle' at part throttle but the springs would be too 'soft' to return the counter-weights to '0' position - especially once the moving parts get sticky.
    I haven't read all the posts so won't comment on other suggestions. Is there an Update on results? Or, is this on another thread?
     
  19. TM1963

    TM1963 Active Member

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    How does it start? Right up or need to crank crank crank?

    I have a similar setup in my 69 Charger - 71 318 block (bored .10 over) , 340 heads (older 2.02 intake), 340 cam (not sure which one, it was free - from a 68 Dart?), 340 intake (Carter AVS carb), double roller timing set. I had a hard time starting it, had to crank the distributor (stock 318 single point) way over - and then couldn't adjust the idle down. I had the distributor in 180 degrees out. Shot fire out of the carb doing that. Put the distributor in right - bingo! (I am a bit fuzzy as I did this 30+ years ago)

    hope it's that easy!
     
  20. Bearhawke

    Bearhawke Things happen for a reason

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    The timing jumping all over the place bothers me as well, that and a possibly sketchy carb.

    Many years ago; I had a 1970's 318 on which I threw on a set of small valve 360 heads, stock Mopar cast iron spreadbore intake and a ca. 1972 Chevy Q-jet carb that I overhauled. Vehicle (1974 B200 van weighing 5,000 lbs) was soft running from the line with its 3:21 gears but; that combo pushed me past 100 MPH. I did that once between inviting a felony speeding ticket if I got stopped and, more importantly, my van was was quite unstable at much over 65 MPH.
     

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